12A Compression issue
03-13-19, 05:18 PM
#1
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12A Compression issue
Hey guys I rebuilt a 12a engine only to end up with a really hard to start rough idling engine. It is not very stable at all. A compression test indicates very consistent 70psi pulses which are low. Is my assumption that may be I cut the side seals too short correct? I don't see the apex or corners being the issue as all of these were brand new and housings are in good condition with no flaking etc. The engine is a half bridge engine.
Any input would be appreciated.
Thanks
Any input would be appreciated.
Thanks
03-13-19, 09:31 PM
#2
Junior Member
Rebuilding a engine and then finding problems with it when you first start it always makes you think the worst. I wouldn't necessarily assume it is a problem with the side seals. Now I haven't yet rebuilt a rotary engine so my knowledge is limited compared to the more senior members on the forum so take my words with a gain of salt. But to me the constancy of the compression between every side of both rotors would indicate that you were consistent with clearancing the side seals. Overlap with the half bridge would also lower the compression reading compared to a more mild port.
Ok with that said I would look into other items that would cause the hard start and idling issues like fuel delivery. Are you getting the right air/fuel mixture at idle? Also the ignition. Are you getting consistent spark to both rotors.
Just food for thought. I hope its helpful.
Ok with that said I would look into other items that would cause the hard start and idling issues like fuel delivery. Are you getting the right air/fuel mixture at idle? Also the ignition. Are you getting consistent spark to both rotors.
Just food for thought. I hope its helpful.
03-13-19, 10:55 PM
#3
Your experience is completely normal. You'll notice at about 500 to1000 miles into break in (keeping it under 4k and light throttle) that the idle will shift into a normal steady state.
EDIT: I lost an apex seal a few months ago and I had to rebuild. After the rebuild my engine would skip a beat at idle... then at about 200 miles after the rebuild the idle smoothed out, no more skipping a beat. These are weird little engines and they require break in periods similar to two stroke motorcycles.
EDIT: I lost an apex seal a few months ago and I had to rebuild. After the rebuild my engine would skip a beat at idle... then at about 200 miles after the rebuild the idle smoothed out, no more skipping a beat. These are weird little engines and they require break in periods similar to two stroke motorcycles.
Last edited by Qingdao; 03-13-19 at 11:00 PM.
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